1. Field of the Invention
The present invention relates generally to commercial, residential and architectural windows and, more particularly, to an integrated multipane window unit and sash assembly and a method for manufacturing the same.
2. Description of the Related Art
As is currently well-known in the art, insulating glass units, or IG units, are currently widely used as elements of windows and doors. Such units are used in windows and doors to reduce heat loss from building interiors in winter, and reduce heat gain into air-conditioned buildings in summer. The insulating glass units are typically formed separate from the sash, and then in a separate step the insulating glass unit is installed in a sash.
IG units generally consist of two parallel sheets of glass which are spaced apart from each other and which have the space between the panes sealed along the peripheries of the panes to enclose an air space between them. Spacer bars are placed along the periphery of the space between the two panes. The spacers are assembled into generally rectangular-shaped frames either by bending or by the use of corner keys.
As has evolved in the present commercially successful technology, insulating glass units form only the internal components of a sash element used in a window unit. A sash element forms the working element of the window, and forms a perimeter called a sash frame that holds necessary working hardware to allow the sash element to slide, lock, crank, etc.
Although many materials of construction are conventionally utilized for manufacturing sash elements, such as wood and aluminum, presently available insulating window units that utilize a sash element formed of extruded polyvinyl chloride polymers are known to provide superior insulating qualities in conventional commercial and residential applications.
In the manufacture of a conventional sash, one starts with an extrusion called a xe2x80x9cprofile.xe2x80x9d These extrusions can be purchased from an extrusion manufacturer in different styles each having a certain aesthetic. Extrusions can be made generally available to the marketplace; however, a general practice that has developed is to provide a partial exclusivity by region, market, etc. in order to allow a particular window manufacturer to associate a certain aesthetic with that manufacturer""s product. Therefore, although many extrusion profiles are of an original design, they are treated in the marketplace as a quasi-commodity.
Another aspect of the extrusion profile is that since the exterior surface must mate with the main frame, the profile is also functional as well as aesthetic. In order to accomplish this functionality, changes are made in internal grooves, channels, etc.
A further step in the manufacture of a sash is to cut corner miters in the sash profile elements used to fabricate the sash frame. These cuts are made in an oversized manner, by xc2xc to xe2x85x9 inch. This additional material is to allow for a process called vinyl welding, in which both seams are heated to a point wherein the PVC material softens and the joint is pressed together and cooled in place to form a cohesive bond. This process forms a corner joint that is stronger than the original extrusion.
The manufacture of the sash results, e.g., in a four-sided sash frame. However, a flash buildup or xe2x80x98swathxe2x80x99 is formed by the vinyl welding process, which must be milled, cut, scraped, or otherwise removed. This process is called corner cleaning, and is generally accomplished by a separate piece of manufacturing equipment called a corner cleaner.
At this point the sash frame is ready for glazing. Glazing is typically accomplished by one of two processes. The first readily used process is when an adhesive strip called a glazing tape is attached to a structure on the profile called the glazing leg. Next, an IG unit (comprising a prefabricated assembly having at least two glazing panes separated by a spacer) is adhered to the other side of the glazing tape. Glazing stops are then placed over the IG unit in order to hold the exterior of the IG unit. This process has advantages, in that the equipment and technology to accomplish this is skewed toward the glazing strip manufacturer, and the window manufacturer can form the window with less equipment and capital outlays. However, the drawbacks to this method lie in the increased cost of and limited materials that can be formed into glazing tapes.
The alternative method of glazing is by a process called back-bedding sealing. In this method, a sash frame is placed horizontally on an X-Y back-bedding machine that will lay down a continuous bead of fluid back bedding sealant along the glazing leg. The prefabricated IG unit is then adhered to the back bedding, and glazing stops are attached. In this method, the back bedding material creates a seal between IG unit and the sash frame. Although additional equipment is required, this process allows the use of a variety of materials, including silicone adhesives, that have advantageous price and/or performance characteristics.
In all cases, IG units must necessarily be manufactured separately, and many times are made by a separate company. The trend is to move this step in-house to control costs, size, availability, etc. Also, by more directly controlling the IG unit manufacture, both retrofit (custom) and standard size (new installation) markets can be addressed.
The manufacturing of conventional IG units, as utilized in the manufacture of PVC insulating windows, has been thoroughly addressed within the art, and is meant to be incorporated herein. For purposes of identifying structures and for providing a frame of reference for the present invention, this manufacture shall be briefly discussed. First, a spacer bar is formed, generally of a hollow, roll-formed flat metal, into a hollow channel. Generally, a desiccant material is placed within the hollow channel, and some provisions are made for the desiccant to come into fluid communication with or otherwise affect the interior space of the IG unit. The spacer bar is then notched in order to allow it to be formed into a rectangular frame. Due to the nature and geometry of this frame, the IG unit at this point has very little structural rigidity. At this point a sealant is applied to the outer three sides of the spacer bar in order to bond a pair of glass panes to either opposite side of the spacer bar. There are a variety of sealants well known in the art that can be used for this purpose. After application of the glass panes and curing of the sealant, the IG unit finally has structural integrity. The current state of the art is represented by U.S. Pat. No. 5,313,761, issued in the name of Leopold, in which hot melt butyl is directly applied to a spacer element that incorporates a folding corner key. Such a method is embodied in a very difficult and clumsy manufacturing process that incorporates a number of inherent manufacturing problems.
A number of other problems exist with the current state of the art in IG unit performance. The use of polyurethane or polysulfide sealants, because of their non-pliable nature when cured, can cause stress fractures of the glass after periods of thermal cycling that cause expansion and contraction of the elements. This leads to fog or moisture intrusion into the interior air space. The use of polyisobutelene sealants have been attempted due to their excellent moisture barrier properties. However, poor structural integrity results. And, although silicone is a strong sealant material, it is porous to moisture intrusion and cannot be used by itself, and must be used as part of a double seal unit (dual seal).
Other recent issues have arisen that have yet to be addressed by the art, and can be characterized by a standard called the xe2x80x9cwarm edge test.xe2x80x9d The warm edge test is a thermal conductivity test that rates the insulating properties the IG unit, and is a method of quantifying the insulating capacity of an assembled insulating window, and not just of the component parts. The driving force for this characterization is governmental regulations that require structures to have certain outside thermal envelope characteristics. However, because of the metal spacer necessary and the inevitable increase in thermal conductance caused by such a structure, conventional IG units perform poorly in this regard. This is mainly due to the fact that conventional IG units were designed to provide insulating properties along the viewable glass area and not increase insulating properties along the perimeter sash and frame areas.
The current state of the art for this technology is also represented by U.S. Pat. No. 5,313,761, issued in the name of Leopold, in which xe2x80x9cUxe2x80x9d shaped spacers without corner keys are used such that conduits for conductive heat transfer are reduced. The elimination of corner keys also eliminates a natural leak point in the system.
A need has been felt for an improved but less complex mechanism that provides a thermally sealed and structurally sealed air pocket bounded on two sides by a glazing pane, for use in otherwise conventional functioning windows.
It has been found that the qualities of well performing thermal air space allow for glazing materials such as glass or plastic (e.g., Plexiglas, a thermoplastic polymer of methyl methacrylate) to expand and contract without stress on the glazing pane to a point where stress fractures would occur; or, to allow sealant to deform to a point where it fails to maintain structural integrity.
Further, it has been found that stresses between the glazing pane and sealant will inevitably take place, and therefore the design of a window sash must allow such stress and movement to occur in a manner that diminishes the full load of such forces on the glazing pane and sealant.
Further, it has been found that the contact of an IG unit with the sash causes the sash to function as a radiator of heat, and consequently, a transmitter of vibration and sound.
Further still, it has been found that the expansion coefficient of glass is less than that of the sash profile extrusion; therefore, any assembly should preferably keep any glass (or other glazing material with a different coefficient of expansion than the sash profile) from making substantial direct contact with the extrusion material, e.g., vinyl.
It would be advantageous to provide methods for fabricating devices of the type disclosed above, which avoid the disadvantages inherent in the state of the art.
It is therefore an object of the invention to provide an improved integrated multipane window unit and sash assembly.
It is another object of the invention to provide an improved method for manufacturing such a multipane window unit.
It is a feature of the present invention to provide an integrated multipane window unit and sash assembly that forms both a thermally sealed and structurally sealed air pocket bounded on two sides by glazing panes, e.g., of glass or plastic, and around its periphery by an internal glazing leg.
It is another feature of the present invention to provide a method for assembling an integrated multipane window unit and sash that allows for glass to expand and contract without stresses that result in failure on either the glass or the sealant.
It is another feature of the present invention to provide an integrated multipane window unit and sash assembly that allows the glazing pane to rest above any extrusion shelf structure, thereby eliminating any stress against the edge of the glass that could cause cracking and providing for water drainage away from the sealant, thereby lessening the opportunity for the sealant to come into contact with water.
It is another feature of the present invention to provide an integrated multipane window unit and sash assembly that includes an offset section in the sash profile that is downward sloping to assist in evacuation of moisture.
It is another feature of the present invention to provide an integrated multipane window unit and sash assembly that allows for the use of a glazing bead (sometimes referred to herein as a glazing clip) in a manner that holds glass in place temporarily while allowing the sealant to cure during the manufacturing process.
It is another feature of the present invention to provide an integrated multipane window unit and sash assembly that utilizes a sealant for both adhesive purposes as well as to form a vapor barrier.
It is another feature of the present invention to provide an integrated multipane window unit and sash assembly that allows the glazing panes to xe2x80x9cfloatxe2x80x9d on sealant, thereby preventing direct contact of glass to the sash profile material.
It is another feature of the present invention to provide an integrated multipane window unit and sash assembly that allows desiccant to be truly isolated from any exterior source, thereby preventing the loading of the desiccant with moisture.
It is another feature of the present invention to provide an integrated multipane window unit and sash assembly that provides added sound deadening characteristics.
It is another feature of the present invention to provide an integrated multipane window unit and sash assembly that allows for the elimination of separately manufactured and installed conventional type IG units.
It is another feature of the present invention to provide a process for manufacturing such an integrated multipane window unit and sash assembly.
Briefly described according to one embodiment of the present invention, an integrated multipane window unit and sash combination is disclosed having a sash frame that incorporates an integral spacing structure formed integrally with the sash frame and protruding toward the viewing opening. The integral spacing structure incorporates internal glazing surfaces upon which adhesive is affixed. In this configuration, the portions of sealant connecting each pane to the sash element are isolated from each other, thereby allowing each piece of glass to function separately.
An advantage of the present apparatus can be readily seen from the present disclosure; however, they can be summarized in the providing of both a superior performing multipane window unit, and an improved method of manufacturing the same.
Briefly described according to one method of manufacturing such an embodiment of the present invention, the use of an integrated multipane window unit and sash combination having integral spacing structure formed integrally with the sash frame and protruding toward the viewing opening allows for an efficient manufacturing process in which the sash can be formed initially in an otherwise conventional manner. Subsequent to the initial forming of a structurally rigid sash member, sealant, either of a structural type, vapor barrier type, a combined type, or both types, can be applied directly to the vertical internal glazing surfaces of the finished sash frame. Next, because the internal glazing surfaces and spacing structure protrude toward the viewing opening, the glass panes can then be affixed to the sealant. At this point, a glazing clip can optionally be affixed in a manner that holds the glass in place temporarily while allowing the sealant to cure during the manufacturing process.
Advantages of the present method can be readily seen from the present disclosure; however, they can be summarized in the providing of such a window unit in a manner that is less capital intensive and requires fewer manufacturing steps, equipment and personnel than what is required to manufacture windows using existing IG units.